This invention relates to devices intended to identify one of a plurality of electrical circuits at a facility, and more particularly to devices of this type which will enable a single worker having access to a distribution center or network to accurately identify and de-energize one of a number of circuits thereat which have extensive inaccessible portions that extend to different remote but accessible locations in the facility, all without requiring the services of an assistant.
In the past various devices and methods have been employed to enable circuits to be identified when visual means cannot be used, or are inconvenient. Three U.S. patents directed to this purpose are U.S. Pat. Nos. 3,076,931; 3,623,142; and 3,924,179, all of which are more or less complicated and moreover do not lend themselves to the specific purpose of the present invention.
In U.S. Pat. No. 3,076,931 the remote ends of a cable being monitored are connected together, and a pulse generator and rotary switch is employed to create different pulses in different lines, which are then discriminated by an inductive pick-up coil so as to identify the desired leads. This arrangement presupposes that the lines in question are not already energized, but instead safe to be worked on and connected to, and that no existing energy of the lines is to be used to generate or effect the pulses.
U.S. Pat. No. 3,623,142 reveals a motor-operated cam that actuates a switch for applying power, through a lamp, to a test lead that is intended to be connected to the questionable lines, one at a time. The remote ends of all the lines to be tested must be grounded so that a pulse can be caused by the switch as it is operated by the cam. Thus, the lines cannot be energized conventionally and tested while carrying power, but instead special "dead" conditions must be established before the testing can be done.
U. S. Pat. No. 3,924,179 proposes using a jumper across the remote ends of a conductor pair, while a pulse is applied to the near end and detected by a clip-on meter. Here, again, the testing cannot be done while the lines are carrying the usual energization, but instead the lines must first be disconnected from all the conventional energy sources prior to the testing.
It has also been proposed to apply a modulated Gaussian noise signal to a line, such as a telephone line, whereby testing can be carried out that is inaudible to persons communicating over the line because the waveforms will only be detected by special receiving equipment.
In connection with electronic instruments such as circuit boards, a test device using a probe has been utilized. The test device has a speaker which emits signals of different tones when the probe is touched to different test points on the board, such tones corresponding to digital "1"s or "0"s, and in some cases comprising alternating high and low pitch sounds.
Other test procedures involve two stations that are respectively connected temporarily to a field unit and an office or central unit, and that communicate with each other electronically to match the corresponding ends of multi-conductor cables which can be of considerable length.
So far as I am aware, no system has been proposed which can, in a simple manner, identify at a central distribution network or point, any of a plurality of live or energized cables that terminate at a remote point, utilizing a pulsing or circuit control device energized from the existing available current in the cables and without requiring the services of additional personnel.
The prior existing or proposed devices were all intended for other purposes, and were never adapted to attain the objectives of the present invention, as well as being more complicated and costly in their constructions.